Kill The Grey-One. He is the horned devils zone in the north. You can hack the MIMIR Z600 to create another target the enemy tries to kill. But it still as likely to to target you as the ghouls.
The only way I can think of to get this battle down to a one one one is to use mindcontrol to pull enemies away from the static guard posts. and yes you can both hogrush and mind-control the grey-one. he just have a tough armor and high HP. He isn't really that special beyond the high tech gun he is carrying. The tough part is that the fight is most likely going to have to deal with many ghouls in the same fight. The MIMIR Z600 isn't a problem it to trigger happy with the flame thrower, which does very little damage to be a major threat. There is an armor on the bottom level near the MIMIR Z600 that you probably want to sneak in and take before the fight.